The present invention relates to a structure design of arbors for boring and milling machines and especially relates to a clamping apparatus that pushes wedges to clamp a boring arbor of a boring and milling machine that use hydraulic force.
Conventional boring and milling machines possess double-layer arbors. These are a milling arbor, and a boring arbor located in the center position of the milling arbor respectively. The boring arbor can make reciprocating motions along the axial direction of the milling arbor so that boring processes can be performed with different depths. Conventionally, two guiding rings are positioned inside the milling arbor which support the boring arbor in sequence. The guiding rings act as a guiding element for the boring arbor when the boring arbor moves. This kind of arbor-setup causes some problems when it is in use: if the stroke of the boring arbor is too large, the nose of the boring arbor will bend down and the associated structure rigidity will not be sufficient. Therefore, the accuracy of the boring processes can be seriously decreased. In an attempt to overcome these problems, different apparatuses for clamping arbors of boring and milling machines were developed, with the principal aim being to tighten the boring arbor so that bending of the boring arbor can be decreased, while increasing the associated structure rigidity of the boring arbor when the boring arbor moves to the required position.
Existing apparatuses for clamping arbors, for example the one proposed by the Japan Patent JP4-176504, comprise principally a hydraulic cylinder and a coned-disk spring placed among the main bearings of the arbors. The operating principles of this arbor clamping apparatus described above are clarified hereinafter: firstly the wedges are automatically pressed by the force induced by the coned-disk spring to tighten the boring arbor. The coned-disk spring and the wedges will be drawn back by the action of the hydraulic cylinder when the boring arbor starts to slide along the axial direction, and then the feed motion of the boring arbor will begin. But this kind of design causes also some problems when it is in use: the friction the O-rings, located between the boring and milling arbors, affects the feeding accuracy of the boring arbor. Further, it is also more difficult to feed hydraulic oil into the hydraulic cylinder when the hydraulic cylinder is placed between the boring and milling arbors and when the boring arbor rotates at high speed.
Another type of arbor clamping apparatus, for example the one proposed by the Japan Patent JP8-197304, is characterized in that the hydraulic cylinder used to clamp the boring arbor is settled in a fixed seat. This fixed seat does not move so that hydraulic oil can be fluently fed into the hydraulic cylinder. A set of bearings is provided, with the piston being positioned inside the hydraulic cylinder. The clamping force induced by the hydraulic cylinder is transmitted by the bearings to the wedges placed among the rotary boring and milling arbors, and is applied together with the reciprocating motion of the hydraulic cylinder to clamp or to slacken the boring arbor. This design has virtually solved the problems caused by the design of the Japan Patent JP4-176504; for example, the advantages of this design are that the inlet for the hydraulic oil source is settled inside the fixed seat such that there is no need to seal the hydraulic oil source at high speed and high pressure surroundings. Of course, at the same time, the O-Rings have also no influence on the feeding accuracy of the boring arbor. But on the other hand, the design of the Japan Patent JP8-197304, also causes some problems; for example, because the hydraulic cylinder is additionally included and occupies the front location of the milling arbor, cutting tools cannot be placed as usual on the front location of the milling arbor.
The principal aim of the present invention is to provide an improved arbor structure for boring and milling machines and the associated clamping apparatus for use in clamping arbors, such that cutting tools of milling can as usual be settled and used while at the same time the problems of low boring accuracy, insufficient structure rigidity and bend of the boring arbor can also be overcame.
The milling arbor proposed by the present invention for boring and milling machines is designed and characterized by two steps spindles, said milling arbor is composed of these two steps spindles wherein the second step spindle is mainly applied to support the boring arbor placed in the center of it, while a hydraulic clamping mechanism is provided with the first step spindle and possesses a fixed shell fixed with the primary body housing of boring and milling machines. Furthermore this fixed shell encloses the outside region of the first step spindle and hence forms a hydraulic chamber. Inside this hydraulic chamber, a piston is established and just by a bearing so the motion of the piston is transmitted to the bearing then to a driving element and this driving element pushes a wedge to move along the axial direction of the boring arbor. Via the approaching action between the boring arbor and the wedge placed among the milling and boring arbors, the clamping for boring arbor is achieved. By the design proposed by the present invention not only the hydraulic driving force can be applied to push the wedges to tighten the boring arbor, but also some tap holes and slots can be provided on the front location of the first step spindle such that large cutting tools of milling and fixtures can be established and utilized.
Further detailed technical setups and embodiments of the present invention are described together with the drawings as follows.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.